Polycrystalline Diamond Constructions Having Improved Thermal Stability

ABSTRACT

Polycrystalline diamond constructions include a diamond body comprising a matrix phase of bonded together diamond crystals formed at high pressure/high temperature conditions with a catalyst material. The sintered body is treated remove the catalyst material disposed within interstitial regions, rendering it substantially free of the catalyst material used to initially sinter the body. Accelerating techniques can be used to remove the catalyst material. The body includes an infiltrant material disposed within interstitial regions in a first region of the construction. The body includes a second region adjacent the working surface and that is substantially free of the infiltrant material. The infiltrant material can be a Group VIII material not used to initially sinter the diamond body. A metallic substrate is attached to the diamond body, and can be the same or different from a substrate used as a source of the catalyst material used to initially sinter the diamond body.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a divisional application of U.S. patentapplication Ser. No. 12/026,398 filed on Feb. 5, 2008, which claimsbenefit of U.S. Provisional Patent Application Nos. 60/888,449 filed onFeb. 6, 2007, and 60/941,616 filed on Jun. 1, 2007, all of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to polycrystalline diamond constructions, andmethods for forming the same, that are specially engineered havingdifferently composed regions for the purpose of providing improvedthermal characteristics when used, e.g., as a cutting element or thelike, during cutting and/or wear applications when compared toconventional PCD comprising the solvent catalyst material used to formthe same.

BACKGROUND OF THE INVENTION

The existence and use polycrystalline diamond material types for formingtooling, cutting and/or wear elements is well known in the art. Forexample, polycrystalline diamond (PCD) is known to be used as cuttingelements to remove metals, rock, plastic and a variety of compositematerials. Such known polycrystalline diamond materials have amicrostructure characterized by a polycrystalline diamond matrix firstphase, that generally occupies the highest volume percent in themicrostructure and that has the greatest hardness, and a plurality ofsecond phases, that are generally filled with a solvent catalystmaterial used to facilitate the bonding together of diamond grains orcrystals together to form the polycrystalline matrix first phase duringsintering.

PCD known in the art is formed by combining diamond grains (that willform the polycrystalline matrix first phase) with a suitable solventcatalyst material (that will form the second phase) to form a mixture.The solvent catalyst material can be provided in the form of powder andmixed with the diamond grains or can be infiltrated into the diamondgrains during high pressure/high temperature (HPHT) sintering. Thediamond grains and solvent catalyst material is sintered at extremelyhigh pressure/high temperature process conditions, during which time thesolvent catalyst material promotes desired intercrystallinediamond-to-diamond bonding between the grains, thereby forming a PCDstructure.

Solvent catalyst materials used for forming conventional PCD includesolvent metals from Group VIII of the Periodic table, with cobalt (Co)being the most common. Conventional PCD can comprise from about 85 to95% by volume diamond and a remaining amount being the solvent metalcatalyst material. The solvent catalyst material is present in themicrostructure of the PCD material within interstices or interstitialregions that exist between the bonded together diamond grains and/oralong the surfaces of the diamond crystals.

The resulting PCD structure produces enhanced properties of wearresistance and hardness, making PCD materials extremely useful inaggressive wear and cutting applications where high levels of wearresistance and hardness are desired. Industries that utilize such PCDmaterials for cutting, e.g., in the form of a cutting element, includeautomotive, oil and gas, aerospace, nuclear and transportation tomention only a few.

For use in the oil production industry, such PCD cutting elements areprovided in the form of specially designed cutting elements such asshear cutters that are configured for attachment with a subterraneandrilling device, e.g., a shear or drag bit. Thus, such PCD shear cuttersare used as the cutting elements in shear bits that drill holes in theearth for oil and gas exploration. Such shear cutters generally comprisea PCD body that is joined to substrate, e.g., a substrate that is formedfrom cemented tungsten carbide. The shear cutter is manufactured usingan HPHT process that generally utilizes cobalt as a catalytic secondphase material that facilitates liquid-phase sintering between diamondparticles to form a single interconnected polycrystalline matrix ofdiamond with cobalt dispersed throughout the matrix.

The shear cutter is attached to the shear bit via the substrate, usuallyby a braze material, leaving the PCD body exposed as a cutting elementto shear rock as the shear bit rotates. High forces are generated at thePCD/rock interface to shear the rock away. In addition, hightemperatures are generated at this cutting interface, which shorten thecutting life of the PCD cutting edge. High temperatures incurred duringoperation cause the cobalt in the diamond matrix to thermally expand andeven change phase (from BCC to FCC), which thermal expansion is known tocause the diamond crystalline bonds within the microstructure to bebroken at or near the cutting edge, thereby also operating to reducesthe life of the PCD cutter. Also, in high temperature oxidizing cuttingenvironments, the cobalt in the PCD matrix will facilitate theconversion of diamond back to graphite, which is also known to radicallydecrease the performance life of the cutting element.

Attempts in the art to address the above-noted limitations have largelyfocused on the solvent catalyst material's degradation of the PCDconstruction by catalytic operation, and removing the catalyst materialtherefrom for the purpose of enhancing the service life of PCD cuttingelements. For example, it is known to treat the PCD body to remove thesolvent catalyst material therefrom, which treatment has been shown toproduce a resulting diamond body having enhanced cutting performance.One known way of doing this involves at least a two-stage technique offirst forming a conventional sintered PCD body, by combining diamondgrains and a solvent catalyst material and subjecting the same to HPHTprocess as described above, and then removing the solvent catalystmaterial therefrom, e.g., by acid leaching process.

Known approaches include removing substantially all of the solventcatalyst material from the PCD body so that the remaining PCD bodycomprises essential a matrix of diamond bonded crystals with no othermaterial occupying the interstitial regions between the diamondcrystals. While the so-formed PCD body may display improved thermalproperties, it now lacks toughness that may make it unsuited forparticular high-impact cutting and/or wear applications. Additionally,it is difficult to attach such so-formed PCD bodies to substrates toform a PCD compact. The construction of a compact having such asubstrate is desired because it enables attachment of the PCD cutter toa cutting and/or wear device by conventional technique, such as welding,brazing or the like. Without a substrate, the so-formed PCD body must beattached to the cutting and/or wear device by interference fit, which isnot practical and does not provide a strong attachment to promote a longservice life.

It is, therefore, desirable that a polycrystalline diamond constructionbe engineered in a manner that not only has improved thermalcharacteristics to provide an improved degree of thermal stability whencompared to conventional PCD, but that does so in a manner that avoidsunwanted deterioration of the PCD body that is known to occur by thepresence of the solvent catalyst material initially used to form the PCDconstruction at or near the working surface. It is further desired thatsuch polycrystalline diamond constructions be engineered in a mannerthat enables the attachment of a substrate thereto, thereby forming athermally stable polycrystalline diamond compact that facilitatesattachment of the polycrystalline diamond compact to cutting and/or weardevices by conventional method, such as by welding, brazing, or thelike.

SUMMARY OF THE INVENTION

Polycrystalline diamond constructions prepared according to principlesof this invention comprise a diamond body having a materialmicrostructure comprising a matrix phase of bonded together diamondcrystals. The diamond bonded matrix phase is formed at highpressure/high temperature conditions in the presence of a catalystmaterial. The diamond body has a surface, e.g., a working surface thatcan be any surface of the diamond body, and includes interstitialregions disposed between the diamond crystals. The diamond body has beentreated so that the interstitial regions previously occupied by thecatalyst material after sintering are empty such that the interstitialregions are substantially free of the catalyst material used toinitially sinter and form the diamond body.

The diamond body comprises a first region that includes an infiltrantmaterial. The infiltrant material can be a Group VIII material and isdisposed within the interstitial regions. In an example embodiment, thefirst region of the diamond body is positioned remote from a diamondbody surface, e.g., a working surface. The diamond body includes asecond region that is positioned adjacent the first region, and thatextends a depth from the diamond body surface, e.g., a working surface.The second region comprises interstitial regions that are substantiallyfree of the infiltrant material. In an example embodiment, the secondregion extends a depth from one or more surfaces of the body includingtop, beveled and/or side surfaces.

The polycrystalline diamond construction can include a substrate that isattached to the diamond body. In an example embodiment, the substratecan be attached to the diamond body adjacent the first region. Thesubstrate that is ultimately attached to the diamond body can be madefrom the same or different material as that which may have been used asa source of the catalyst material during the initial process of formingthe diamond bonded matrix phase.

Such polycrystalline diamond constructions can be made by subjectingdiamond grains to a high pressure/high temperature condition in thepresence of a catalyst material to form the polycrystalline diamondmaterial comprising the matrix phase of bonded together diamond grainsand interstitial regions disposed between the diamond grains includingthe catalyst material. The so-formed sintered diamond material istreated to remove the catalyst material therefrom, producing a diamondbody that is substantially free of the catalyst material used toinitially form the polycrystalline diamond material. An infiltrantmaterial is introduced into the diamond body, filling at least apopulation of the otherwise empty interstitial regions resulting fromthe removal of the catalyst material. It is desired that a region of thediamond body remain substantially free of the infiltrant material. Ametallic substrate can then be attached to the diamond body.

Polycrystalline diamond constructions, prepared according to principlesof this invention being substantially free of the catalyst material usedto initially form the diamond body, display properties of improvedthermal stability when compared to conventional PCD. Further,polycrystalline diamond constructions of this invention, comprising aregion that includes an infiltrant material, permit formation of acompact comprising a substrate that facilitates attachment with end-usecutting, wearing, and machine devices for desired end-use applicationsby conventional methods such as by welded or brazed attachment.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the present invention will beappreciated as the same becomes better understood by reference to thefollowing detailed description when considered in connection with theaccompanying drawings wherein:

FIG. 1A is a schematic view of a region taken from a polycrystallinediamond body comprising an infiltrant material disposed interstitiallybetween bonded together diamond crystals;

FIG. 1B is a schematic view of a region taken from a polycrystallinediamond body that is substantially free of the infiltrant material ofFIG. 1;

FIGS. 2A to 2H are cross-sectional schematic side views ofpolycrystalline diamond constructions of this invention during differentstages of formation;

FIG. 3 is a schematic side view of an example embodiment polycrystallinediamond compact construction of this invention comprising a substrate;

FIG. 4 is a perspective side view of an insert, for use in a roller coneor a hammer drill bit, comprising polycrystalline diamond constructionsof this invention;

FIG. 5 is a perspective side view of a roller cone drill bit comprisinga number of the inserts of FIG. 4;

FIG. 6 is a perspective side view of a percussion or hammer bitcomprising a number of inserts of FIG. 4;

FIG. 7 is a schematic perspective side view of a diamond shear cuttercomprising the polycrystalline diamond constructions of this invention;and

FIG. 8 is a perspective side view of a drag bit comprising a number ofthe shear cutters of FIG. 7.

DETAILED DESCRIPTION

Polycrystalline diamond constructions of this invention have a materialmicrostructure comprising a polycrystalline matrix first phase that isformed from bonded together diamond grains or crystals. The diamond bodyfurther includes interstitial regions disposed between the diamondcrystals, wherein in one region of the body the interstitial regions arefilled with an infiltrant material that was not used to initially formthe diamond body, and wherein in another region of the body theinterstitial regions are substantially free of the infiltrant material.The construction can additionally comprise one or more substrate that isattached to the diamond body, thereby forming a compact construction.

Such polycrystalline diamond constructions and compacts configured inthis matter are specially engineered to provide improved thermalcharacteristics such as thermal stability when exposed to cutting andwear applications when compared to conventional PCD materials, i.e.,those that are formed from and that include the catalyst material, e.g.,a solvent metal catalyst, that was initially used to form the diamondbody. Polycrystalline diamond constructions of this invention,comprising a substrate attached thereto, facilitate attachment of theconstruction to desired tooling, cutting, machining, and/or weardevices, e.g., a drill bit used for drilling subterranean formations.

As used herein, the term “polycrystalline diamond” refers to a materialthat has been formed at high pressure/high temperature (HPHT) conditionsthat has a material microstructure comprising a matrix phase ofbonded-together diamond crystals and that is substantially free of thecatalyst material that was used to initially form the matrix diamondphase. The material microstructure further includes a plurality ofinterstitial regions that are disposed between the diamond crystals.Polycrystalline diamond constructions of this invention can be formed byconventional method of subjecting precursor diamond grains or powder toHPHT sintering conditions in the presence of a catalyst material, e.g.,a solvent metal catalyst, that functions to facilitate the bondingtogether of the diamond grains at temperatures of between about 1,350 to1,500° C., and pressures of 5,000 Mpa or higher. Suitable catalystmaterials useful for making PCD include those metals identified in GroupVIII of the Periodic table.

As used herein, the term “thermal characteristics” is understood torefer to characteristics that impact the thermal stability of theresulting polycrystalline construction, which can depend on such factorsas the relative thermal compatibilities such as thermal expansionproperties, of the materials occupying the different constructionmaterial phases.

A feature of polycrystalline constructions of this invention is thatthey comprise a diamond body that retains the matrix phase of bondedtogether diamond crystals, but the body has been modified so that it nolonger includes the catalyst material that was used during the sinteringprocess to initially form the body of bonded diamonds and that remainsfrom that sintering process. Rather, the diamond body has been speciallytreated so that such catalyst material is removed from the interstitialregions of the diamond body. The diamond body is subsequently treated sothat the empty interstitial regions in one region comprise an infiltrantmaterial, while the interstitial regions in another region remain emptyor are substantially free of the infiltrant material.

As used herein, the term “infiltrant material” is understood to refer tomaterials that are other than the catalyst material that was used toinitially form the diamond body, and can include materials identified inGroup VIII of the Periodic table that have subsequently been introducedinto the sintered diamond body after the catalyst material used to formthe same has been removed therefrom. Additionally, the term “infiltrantmaterial” is not intended to be limiting on the particular method ortechnique use to introduce such material into the already formed diamondbody.

FIG. 1A schematically illustrates a region 10 of a polycrystallinediamond construction prepared according to principles of this inventionthat includes the infiltrant material. Specifically, the region 10includes a material microstructure comprising a plurality of bondedtogether diamond crystals 12, forming an intercrystalline diamond matrixfirst phase, and the infiltrant material 14 that is interposed withinthe plurality of interstitial regions that exist between the bondedtogether diamond crystals and/or that are attached to the surfaces ofthe diamond crystals. For purposes of clarity, it is understood that theregion 10 of the polycrystalline construction is one taken from adiamond body after it has been modified in accordance with thisinvention to remove the catalyst material that was used to initiallyform the diamond body.

FIG. 1B schematically illustrates a region 22 of a polycrystallinediamond construction prepared according to principles of this inventionthat is substantially free of the infiltrant material. Like thepolycrystalline diamond construction region illustrated in FIG. 1A, theregion 22 includes a material microstructure comprising the plurality ofbonded together diamond crystals 24, forming the intercrystallinediamond matrix first phase. Unlike the region 10 illustrated in FIG. 1A,this region of the diamond body 22 has been modified to remove theinfiltrant material from the plurality of interstitial regions and, thuscomprises a plurality of interstitial regions 26 that are substantiallyfree of the infiltrant material. Again, it is understood that the region22 of the polycrystalline diamond construction is one taken from adiamond body after it has been modified according to principles of thisinvention to remove the catalyst material that was used to initiallyform the diamond body therefrom.

Polycrystalline diamond constructions of this invention are provided inthe form of a diamond body that may or may not be attached to asubstrate. The diamond body may be configured to include the twoabove-described regions in the form of two distinct portions of thebody, or the diamond body can be configured to include the twoabove-described regions in the form of discrete elements that arepositioned at different locations within the body, depending on theparticular end-use application.

Polycrystalline diamond constructions configured in this manner, lackingthe catalyst material used to initially form the diamond body and thatis further modified to include the two regions described above, provideimproved thermal characteristics to the resulting materialmicrostructure when compared to conventional PCD comprising the catalystmaterial that was used to initially form the diamond body.

FIGS. 2A, 2B, and 2C each schematically illustrate an example embodimentpolycrystalline diamond construction 30 of this invention at differentstages of formation. FIG. 2A illustrates a first stage of formation,starting with a conventional PCD body 32 in its initial form aftersintering by conventional HPHT sintering process. At this early stage,the PCD body 32 comprises a polycrystalline diamond matrix phase and asolvent catalyst metal material, such as cobalt, used to form thediamond matrix phase and that is disposed within the interstitialregions between the bonded together diamond crystals forming the matrixphase. The solvent catalyst metal material can be added to the precursordiamond grains or powder as a raw material powder prior to sintering, itcan be contained within the diamond grains or powder, or it can beinfiltrated into the diamond grains or powder during the sinteringprocess from a substrate containing the solvent metal catalyst materialand that is placed adjacent the diamond powder and exposed to the HPHTsintering conditions. In an example embodiment, the solvent metalcatalyst material is provided as an infiltrant from a substrate 34,e.g., a WC—Co substrate, during the HPHT sintering process.

Diamond grains useful for forming the PCD body include synthetic ornatural diamond powders having an average diameter grain size in therange of from submicrometer in size to 100 micrometers, and morepreferably in the range of from about 1 to 80 micrometers. The diamondpowder can contain grains having a mono or multi-modal sizedistribution. In the event that diamond powders are used havingdifferently sized grains, the diamond grains are mixed together byconventional process, such as by ball or attritor milling for as muchtime as necessary to ensure good uniform distribution.

As noted above, the diamond powder may be combined with a desiredsolvent metal catalyst powder to facilitate diamond bonding during theHPHT process and/or the solvent metal catalyst can be provided byinfiltration from a substrate positioned adjacent the diamond powderduring the HPHT process. Suitable solvent metal catalyst materialsuseful for forming the PCD body include those metals selected from GroupVIII elements of the Periodic table. A particularly preferred solventmetal catalyst is cobalt (Co),

Alternatively, the diamond powder mixture can be provided in the form ofa green-state part or mixture comprising diamond powder that iscontained by a binding agent, e.g., in the form of diamond tape or otherformable/confirmable diamond mixture product to facilitate themanufacturing process. In the event that the diamond powder is providedin the form of such a green-state part it is desirable that a preheatingstep take place before HPHT consolidation and sintering to drive off thebinder material. In an example embodiment, the PCD body resulting fromthe above-described HPHT process may have a diamond volume content inthe range of from about 85 to 95 percent. For certain applications, ahigher diamond volume content up to about 98 percent may be desired.

The diamond powder or green-state part is loaded into a desiredcontainer for placement within a suitable HPHT consolidation andsintering device. In an example embodiment, where the source of thesolvent metal catalyst material is provided by infiltration from asubstrate, a suitable substrate material is disposed within theconsolidation and sintering device adjacent the diamond powder mixture.In a preferred embodiment, the substrate is provided in a preformedstate. Substrates useful for forming the PCD body can be selected fromthe same general types of materials conventionally used to formsubstrates for conventional PCD materials, including carbides, nitrides,carbonitrides, ceramic materials, metallic materials, cermet materials,and mixtures thereof. A feature of the substrate used for forming thePCD body is that it includes a solvent metal catalyst capable of meltingand infiltrating into the adjacent volume of diamond powder tofacilitate conventional diamond-to-diamond intercrystalline bondingforming the PCD body. A preferred substrate material is cementedtungsten carbide (WC—Co).

Where the solvent metal catalyst is provided by infiltration from asubstrate, the container including the diamond power and the substrateis loaded into the HPHT device and the device is then activated tosubject the container to a desired HPHT condition to effectconsolidation and sintering of the diamond powder. In an exampleembodiment, the device is controlled so that the container is subjectedto a HPHT process having a pressure of 5,000 Mpa or more and atemperature of from about 1,350° C. to 1,500° C. for a predeterminedperiod of time. At this pressure and temperature, the solvent metalcatalyst melts and infiltrates into the diamond powder, therebysintering the diamond grains to form conventional PCD.

While a particular pressure and temperature range for this HPHT processhas been provided, it is to be understood that such processingconditions can and will vary depending on such factors as the typeand/or amount of solvent metal catalyst used in the substrate, as wellas the type and/or amount of diamond powder used to form the PCD body orregion. After the HPHT process is completed, the container is removedfrom the HPHT device, and the assembly comprising the bonded togetherPCD body and substrate is removed from the container. Again, it is to beunderstood that the PCD body can be formed without using a substrate ifso desired.

FIG. 2B schematically illustrates an example embodiment polycrystallinediamond construction 30 of this invention after a second stage offormation, specifically at a stage where the solvent catalyst materialused to initially form the diamond body and disposed in the interstitialregions and/or attached to the surface of the bonded together diamondcrystals has been removed form the diamond body 32. At this stage ofmaking the construction, the diamond body has a material microstructureresembling region 22 that is illustrated in FIG. 1B, comprising thediamond matrix phase formed from a plurality of bonded together diamondcrystals 24, and interstitial regions 26 that are substantially free ofthe specific catalyzing material, e.g., cobalt, that was used during thesintering process to initially form the body of bonded diamonds and thatremains from that sintering process used to initially form the diamondmatrix phase.

As used herein, the term “removed” is used to refer to the reducedpresence of the specific catalyst material in the diamond body that wasused to initially form the diamond body during the sintering or HPHTprocess, and is understood to mean that a substantial portion of thecatalyst material no longer resides within the diamond body. However, itis to be understood that some small trace amounts of the catalystmaterial may still remain in the microstructure of the diamond bodywithin the interstitial regions and/or adhered to the surface of thediamond crystals. Additionally, the term “substantially free”, as usedherein to refer to the remaining diamond body after the specificcatalyst material used to form it during sintering has been removed, isunderstood to mean that there may still be some trace small amounts ofthe specific metal catalyst remaining within the diamond body as notedabove.

The quantity of the specific catalyst material used to form the diamondbody remaining in the material microstructure after the diamond body hasbeen subjected to treatment to remove the same can and will vary on suchfactors as the efficiency of the removal process, and the size anddensity of the diamond matrix material. In an example embodiment, thecatalyst material used to form the diamond body is removed therefrom bya suitable process, such as by chemical treatment such as by acidleaching or aqua regia bath, electrochemically such as by electrolyticprocess, by liquid metal solubility technique, by liquid metalinfiltration technique that sweeps the existing second phase materialaway and replaces it with another during a liquid-phase sinteringprocess, or by combinations thereof. In an example embodiment, thecatalyst material is removed from all or a desired region of the PCDbody by an acid leaching technique, such as that disclosed for examplein U.S. Pat. No. 4,224,380, which is incorporated herein by reference.

Accelerating techniques for removing the catalyst material can also beused, and can be used in conjunction with the leaching techniques notedabove as well as with other conventional leaching processing. Suchaccelerating techniques include elevated pressures, elevatedtemperatures and/or ultrasonic energy, and can be useful to decrease theamount of treatment time associated with achieving the same level ofcatalyst removal, thereby improving manufacturing efficiency.

In one embodiment, the leaching process can be accelerated by conductingthe same under conditions of elevated pressure that may be greater thanabout 5 bar, and that may range from about 10 to 50 bar in otherembodiments. Such elevated pressure conditions can be achieved byconducting the leaching process in a pressure vessel or the like. It isto be understood that the exact pressure condition can and will vary onsuch factors as the leaching agent that is used as well as the materialsand sintering characteristics of the diamond body.

In addition to elevated pressure, elevated temperatures can also be usedfor the purpose of accelerating the leaching process. Suitabletemperature levels may be in the range of from about 90 to 350° C. inone embodiment, and up to 175 to 225° C. in another embodiment. In oneor more embodiments, elevated temperature levels may range up to 300° C.It is to be understood that the exact temperature condition can and willvary on such factors as the leaching agent that is used as well as thematerials and sintering characteristics of the diamond body. It is to beunderstood that the accelerating technique can include elevated pressurein conjunction with elevated temperature, which would involve the use ofa pressure assembly capable of producing a desired elevated temperature,e.g., by microwave heating or the like. For example, amicrowave-transparent pressure vessel can be issued to implement theaccelerated leaching process. Alternatively, the accelerating techniquecan include elevated temperature or elevated pressure, i.e., one or theother and not a combination of the two.

Ultrasonic energy can be used as an accelerating technique that involvesproviding vibratory energy operating at frequencies beyond audiblesound, e.g., at frequencies of about 18,000 cycles per second andgreater. A converter or piezoelectronic transducer can be used for forma desired ultrasonic stack for this purpose, wherein the piezoelectriccrystals are used to convert electrical charges to desired acousticenergy, i.e., ultrasonic energy. Boosters can be used to modify theamplitude of the mechanical vibration, and a sontotrode or horn can beused to apply the vibration energy. The use of ultrasonic energy canproduce an 80 to 90 percent increase in leaching depth as a function oftime as compared to leaching without using ultrasonic energy, therebyproviding a desired decrease in leaching time and an improvement inmanufacturing efficiency.

Referring again to FIG. 2B, at this stage of the process any substrate34 that was used as a source of the catalyst material can be removedfrom the diamond body 32, and/or may fall away from the diamond bodyduring the process of catalyst material removal. In an exampleembodiment, it may be desired to remove the substrate from the diamondbody before treatment to facilitate the catalyst removal process, e.g.,so that all surfaces of the diamond body can be exposed for the purposeof catalyst material removal. If the catalyst material was mixed with orotherwise provided with the precursor diamond powder, then thepolycrystalline construction 30 at this stage of manufacturing will notcontain a substrate, i.e., it will only consist of a diamond body 32.

FIG. 2C schematically illustrates an example embodiment polycrystallineconstruction 30 prepared according to principles of this invention aftera third stage of formation. Specifically, at a stage where the catalystmaterial used to initially form the diamond body has been removedtherefrom and has been replaced with a desired infiltrant material. Inthe example embodiment noted above, the infiltrant material can beselected from the group of materials including metals, ceramics,cermets, and combinations thereof. In an example embodiment, theinfiltrant material is a metal or metal alloy selected from Group VIIIof the Periodic table, such as cobalt, nickel, iron or combinationsthereof. It is to be understood that the choice of material or materialsused as the infiltrant material can and will vary depending on suchfactors including but not limited to the end-use application, and thetype and density of the diamond grains used to form the polycrystallinediamond matrix first phase, and the mechanical properties and/or thermalcharacteristics desired for the polycrystalline diamond construction.

Referring back to FIG. 2B, once the catalyst material used to initiallyform the diamond body is removed from the diamond body, the remainingmicrostructure comprises a polycrystalline matrix phase with a pluralityof interstitial voids 26 forming what is essentially a porous materialmicrostructure. This porous microstructure not only lacks mechanicalstrength, but also lacks a material constituent that is capable offorming a strong attachment bond with a substrate, e.g., in the eventthat the polycrystalline diamond construction needs to be in the form ofa compact comprising such a substrate to facilitate attachment to anend-use device.

The voids or pores in the polycrystalline diamond body can be filledwith the infiltrant material using a number of different techniques.Further, all of the voids or only a portion of the voids in the diamondbody can be filled with the replacement material. In an exampleembodiment, the infiltrant material can be introduced into the diamondbody by liquid-phase sintering under HPHT conditions. In such exampleembodiment, the infiltrant material can be provided in the form of asintered part or a green-state part that contains the infiltrantmaterial and that is positioned adjacent one or more surfaces of thediamond body. The assembly is placed into a container that is subjectedto HPHT conditions sufficient to melt the infiltrant material within thesintered part or green-state part and cause it to infiltrate into thediamond body. In an example embodiment, the source of the infiltrantmaterial can be a substrate that will be used to form a compact from thepolycrystalline diamond construction by attachment to the diamond bodyduring the HPHT process.

Alternatively, rather than using a substrate as a source of theinfiltrant material, the diamond body can be encapsulated with a desiredpower mixture, e.g., one formed from one or more materials that can besintered to provide a material that is attached to the diamond body andthat has desired properties to facilitate use of the resulting sinteredpolycrystalline diamond construction in a cutting and/or wearapplication. For example, the powder mixture can comprise a WC-co/alloy.When subjected to HPHT conditions, the cobalt in such powder mixturewill melt and infiltrate into the diamond body from all directions.Additionally, any remaining material outside of the diamond body may besintered and attached to the diamond body.

Alternatively, the infiltrant material can be introduced into the PCDbody by pressure technique where the infiltrant material is provided inthe form of a slurry or the like comprising a desired infiltrantmaterial with a carrier, e.g., such as a polymer or organic carrier. Theslurry is then exposed to the diamond body at high pressure to cause itto enter the diamond body and cause the infiltrant material to fill thevoids therein. The PCD body can then be subjected to elevatedtemperature for the purpose of removing the carrier therefrom, therebyleaving the replacement material disposed within the interstitialregions.

The term “filled”, as used herein to refer to the presence of theinfiltrant material in the voids or pores of the diamond body thatresulted from removing the catalyst material used to form the diamondbody therefrom, is understood to mean that a substantial volume of suchvoids or pores contain the infiltrant material. However, it is to beunderstood that there may also be a volume of voids or pores within thesame region of the diamond body that do not contain the infiltrantmaterial, and that the extent to which the infiltrant materialeffectively displaces the empty voids or pores will depend on suchfactors as the particular microstructure of the diamond body, theeffectiveness of the process used for introducing the infiltrantmaterial, and the desired mechanical and/or thermal properties of theresulting polycrystalline diamond construction. In a preferredembodiment, when introduced into the diamond body, the infiltrantsubstantially fills all of the voids or pores within the diamond body.In some embodiments, complete migration of the infiltrant materialthrough the diamond body may not be realized, in which case a region ofthe diamond body may not include the infiltrant material. This regiondevoid of the infiltrant material from such incomplete migration mayextend from the region comprising the infiltrant to a surface portion ofthe diamond body.

In an example embodiment, a substrate is used as the source of theinfiltrant material and to form the polycrystalline construction.Substrates useful in this regard can include substrates that are used toform conventional PCD, e.g., those formed from metals, ceramics, and/orcermet materials that contain a desired infiltrant. In an exampleembodiment, the substrate is formed from WC—Co, and is positionedadjacent the diamond body after the metal catalyst material used toinitially form the same been removed, and the assembly is subjected toHPHT conditions sufficient to cause the cobalt in the substrate to meltand infiltrate into and fill the voids or pores in the polycrystallinediamond matrix.

The substrate used as a source for the infiltrant material can have amaterial make up and/or performance properties that are different fromthat of a substrate used to provide the catalyst material for theinitial sintering of the diamond body. For example, the substrateselected for sintering the diamond body may comprise a material make upthat facilitates diamond bonding, but that may have poor erosionresistance and as a result not be well suited for an end-use applicationin a drill bit. In this case, the substrate selected at this stage forproviding the source of the infiltrant can be selected from materialsdifferent from that of the sintering substrate, e.g., from materialscapable of providing improved down hole properties such as erosionresistance when attached to a drill bit. Accordingly, it is to beunderstood that the substrate material selected as the infiltrant sourcecan be different from the substrate material used to initially sinterthe diamond body.

In an example embodiment, wherein a PCD material is treated to removethe solvent metal catalyst material, Co, used to initially form the sametherefrom, the resulting diamond body was subjected to further HPHTprocessing for a period of approximately 100 seconds at a temperaturesufficient to meet the melting temperature of the infiltrant material,which was cobalt. The source of the cobalt infiltrant material was aWC—Co substrate that was positioned adjacent a desired surface portionof the diamond body prior to HPHT processing. The HPHT process wascontrolled to bring the contents to the melting temperature of cobalt(about 1,350° C., at a pressure of about 3,400 to 7,000 Mpa) to enablethe cobalt to infiltrate into and fill the pores or voids in the diamondbody. During the HPHT process, the substrate containing the cobaltmaterial was attached to the diamond body to thereby form apolycrystalline diamond compact construction.

In addition to the representative processes for introducing theinfiltrant material into the voids or pores of the diamond body, otherprocesses can be used for introducing the infiltrant material. Theseprocesses include, but are not limited to chemical processes,electrolytic processes, and by electro-chemical processes.

FIG. 2C illustrates the diamond body 32 at a stage when it is filledwith the infiltrant material, wherein the diamond body is free standing.However, as mentioned above, it is to be understood that the diamondbody 32 filled with the infiltrant material at this stage of processingcan be in the form of a compact construction comprising a substrateattached thereto. The substrate can be attached during the HPHT processused to fill the diamond body with the infiltrant material.Alternatively, the substrate can be attached separately from the HPHTprocess used for filling, such as by a separate HPHT process, or byother attachment technique such as brazing or the like.

Once the diamond body 32 has been filled with the infiltrant material,it is then treated to remove a portion of the infiltrant materialtherefrom. Alternatively, if the infiltrant material did not migratecompletely through the diamond body, a subsequent infiltrant removalstep may not be necessary, or may useful as a clean up process to ensurea uniform infiltrant removal depth.

FIGS. 2D, 2E, 2F and 2G all illustrate representative embodiments ofdiamond bodies that have been filled with the infiltrant material andsubsequently treated to remove the infiltrant material from a regiontherefrom. Techniques useful for removing a portion of the infiltrantmaterial from the diamond body includes the same ones described abovefor removing the catalyst material used to initially form the diamondbody from the PCD material, e.g., during the second step of processingsuch as by acid leaching or the like. In an example embodiment, it isdesired that the process of removing the infiltrant material becontrolled so that the infiltrant material be removed from a targetedregion of the diamond body extending a determined depth from one or morediamond body surfaces. These surfaces may include working and/ornonworking surfaces of the diamond body.

In an example embodiment, the infiltrant material is removed from thediamond body a depth of less than about 0.5 mm from the desired surfaceor surfaces, and preferably in the range of from about 0.05 to 0.4 mm.Ultimately, the specific depth of the region formed in the diamond bodyby removing the infiltrant material will vary depending on theparticular end-use application.

FIG. 2D illustrates an embodiment of the polycrystalline diamondconstruction 30 comprising the diamond body 32 that includes a firstregion 36 that is substantially free of the infiltrant material, and asecond region 38 that includes the infiltrant material. The first region36 extends a depth from surfaces 40 and 42 of the PCD body, and thesecond region 38 is remote from the surfaces 40 and 42. In thisparticular embodiment, the surfaces include a top surface 40 and sidesurfaces 42 of the diamond body. The depth of the first regions can bethe same or different for the surfaces 40 and 42 depending on theparticular end-use application. Additionally, the extent of the sidesurfaces that include the first region can vary from extending along theentire side of the diamond body to extending only along a partial lengthof the side of diamond body.

FIG. 2E illustrates an embodiment of the polycrystalline diamondconstruction 30 that is similar to that illustrated in FIG. 2D, exceptthat it includes a beveled or chamfered surface 44 that is positionedalong an edge of the diamond body 32, between the top surface 40 and theside surface 42, and that includes the first region. The beveled surfacecan be formed before or after the PCD body has been treated to form thefirst region 36. In a preferred embodiment, the beveled region is formedbefore the PCD body has been treated to form the first region, e.g., byOD grinding or the like.

FIG. 2F illustrates another embodiment of the polycrystalline diamondconstruction 30 of this invention that is similar to that illustrated inFIG. 2D, except that the first region 36 is positioned only along theside surface 42 of the diamond body 32 and not along the top surface 40.Thus, in this particular embodiment, the first region is in the form ofan annular region that surrounds the second region 38. Again, it is tobe understood that the placement position of the first region relativeto the second region can and will vary depending on the particularend-use application.

FIG. 2G illustrates another embodiment of the polycrystalline diamondconstruction 30 of this invention that is similar to that illustrated inFIG. 2D except that the first region 36 is positioned only along the topsurface 40 of the diamond body 32 and not along the side surface 42.Thus, in this particular embodiment, the first region is in the form ofa disk-shaped region on top of the second region 38.

FIG. 2H illustrates an embodiment of the polycrystalline construction 30comprising the diamond body 32 as illustrated in FIG. 2D attached to adesired substrate 44, thereby forming a polycrystalline diamond compactconstruction 46. As noted above, the substrate 44 can be attached to thediamond body 32 during the HPHT process that is used during the thirdstep of making the polycrystalline diamond construction, e.g., tointroduce the infiltrant material into the diamond body. Alternatively,the infiltrant material can be added to the diamond body independent ofa substrate, in which case the desired substrate can be attached to thediamond body by either a further HPHT process or by brazing, welding, orthe like. FIG. 3 illustrates a side view of the polycrystalline diamondconstruction 30 of FIG. 2H, provided in the form of a compact comprisingthe diamond body 32 attached to the substrate 44.

In an example embodiment, the substrate used to form the polycrystallinediamond compact construction is formed from a cermet material, such asthat conventionally used to form a PCD compact. In a preferredembodiment, when the substrate is used as the source of the replacementmaterial, the substrate is formed from a cermet, such as a WC, furthercomprising a binder material that is the infiltrant material used tofill the diamond body. Suitable binder materials include Group VIIImetals of the Periodic table or alloys thereof, and/or Group IB metalsof the Periodic table or alloys thereof, and/or other metallicmaterials.

Although the substrate may be attached to the diamond body during theinfiltrant material introduction, it is also understood that thesubstrate may be attached to the diamond body after the desiredinfiltrant material has been introduced. In such case, infiltrantmaterial can be introduced into the diamond body by a HPHT process thatdoes not use the substrate material as a source, and the desiredsubstrate can be attached to the diamond body by a separate HPHT processor other method, such as by brazing, welding or the like. The substratecan further be attached to the diamond body before or after theinfiltrant material has been partially removed therefrom.

If desired, an intermediate material can be interposed between thesubstrate and the diamond body. The intermediate material can be formedfrom those materials that are capable of forming a suitable attachmentbond between both the diamond body and the substrate. In the event thatthe substrate material includes a binder material that is a Group VIIIelement, it is additionally desired that the intermediate materialoperate as a barrier to prevent or minimize the migration of thesubstrate binder material into the diamond body during the attachmentprocess. Suitable intermediate materials include those described aboveas being useful as the replacement material, e.g., can be anoncatalyzing material, and/or can have a melting temperature that isbelow the melting temperature of any binder material in the substrate.Suitable intermediate materials can be cermet materials comprising anoncatalyzing material such as WC—Cu, WC—Cu alloy, or the like.

Although the interface between the diamond body and the substrateillustrated in FIG. 2H are shown as having a planar geometry, it isunderstood that this interface can also have a nonplanar geometry, e.g.,having a convex configuration, a concave configuration, or having one ormore surface features that project from one or both of the diamond bodyand substrate. Such a nonplanar interface may be desired for the purposeof enhancing the surface area of contact between the attached diamondbody and substrate, and/or for the purpose of enhancing heat transfertherebetween, and/or for the purpose of reducing the degree of residualstress imposed on the diamond body. Additionally, the diamond bodysurfaces can be configured differently than that illustrated in FIGS. 2Ato 2H, having a planar or nonplanar geometry.

Further, polycrystalline diamond constructions of this invention maycomprise a diamond body having properties of diamond density and/ordiamond grain size that change as a function of position within thediamond body. For example, the diamond body may have a diamond densityand/or a diamond grain size that changes in a gradient or step-wisefashion moving away from a working surface of the diamond body. Further,rather than being formed as a single mass, the diamond body used informing polycrystalline diamond constructions of this invention can beprovided in the form of a composite construction formed from a number ofdiamond bodies that have been combined together, wherein each such bodycan have the same or different properties such as diamond grain size,diamond density, or the like.

Polycrystalline diamond constructions of this invention display markedimprovements in thermal stability and thus service life when compared toconventional PCD materials that comprise the catalyst material used toinitially form the same. Polycrystalline diamond constructions of thisinvention can be used to form wear and/or cutting elements in a numberof different applications such as the automotive industry, the oil andgas industry, the aerospace industry, the nuclear industry, and thetransportation industry to name a few. Polycrystalline diamondconstructions of this invention are well suited for use as wear and/orcutting elements that are used in the oil and gas industry in suchapplication as on drill bits used for drilling subterranean formations.

FIG. 4 illustrates an embodiment of a polycrystalline diamond compactconstruction of this invention provided in the form of an insert 70 usedin a wear or cutting application in a roller cone drill bit orpercussion or hammer drill bit used for subterranean drilling. Forexample, such inserts 70 can be formed from blanks comprising asubstrate 72 formed from one or more of the substrate materials 73disclosed above, and a diamond body 74 having a working surface 76comprising a material microstructure made up of the polycrystallinediamond matrix phase, a first region comprising the infiltrant material,and a second region that is substantially free of the infiltrantmaterial, wherein the first and second regions are positioned within theinterstitial regions of the matrix phase. The blanks are pressed ormachined to the desired shape of a roller cone rock bit insert.

Although the insert in FIG. 4 is illustrated having a generallycylindrical configuration with a rounded or radiused working surface, itis to be understood that inserts formed from polycrystallineconstructions of this invention configured other than as illustrated andsuch alternative configurations are understood to be within the scope ofthis invention.

FIG. 5 illustrates a rotary or roller cone drill bit in the form of arock bit 78 comprising a number of the wear or cutting inserts 70disclosed above and illustrated in FIG. 4. The rock bit 78 comprises abody 80 having three legs 82, and a roller cutter cone 84 mounted on alower end of each leg. The inserts 70 can be fabricated according to themethod described above. The inserts 70 are provided in the surfaces ofeach cutter cone 84 for bearing on a rock formation being drilled.

FIG. 6 illustrates the inserts 70 described above as used with apercussion or hammer bit 86. The hammer bit comprises a hollow steelbody 88 having a threaded pin 90 on an end of the body for assemblingthe bit onto a drill string (not shown) for drilling oil wells and thelike. A plurality of the inserts 70 is provided in the surface of a head92 of the body 88 for bearing on the subterranean formation beingdrilled.

FIG. 7 illustrates a polycrystalline construction compact of thisinvention embodied in the form of a shear cutter 94 used, for example,with a drag bit for drilling subterranean formations. The shear cutter94 comprises a diamond body 96, comprising the polycrystalline diamondmatrix phase, a first phase comprising the infiltrant material, and asecond phase that is substantially free of the infiltrant material,wherein the first and second phases are positioned within theinterstitial regions of the matrix. The body is attached to a cuttersubstrate 98. The PCD body 96 includes a working or cutting surface 100.

Although the shear cutter in FIG. 7 is illustrated having a generallycylindrical configuration with a flat working surface that is disposedperpendicular to an axis running through the shear cutter, it is to beunderstood that shear cutters formed from polycrystalline diamondconstructions of this invention can be configured other than asillustrated and such alternative configurations are understood to bewithin the scope of this invention.

FIG. 8 illustrates a drag bit 102 comprising a plurality of the shearcutters 94 described above and illustrated in FIG. 7. The shear cuttersare each attached to blades 104 that each extend from a head 106 of thedrag bit for cutting against the subterranean formation being drilled.

Other modifications and variations of polycrystalline diamond bodies,constructions, compacts, and methods of forming the same according tothe principles of this invention will be apparent to those skilled inthe art. For example, prior to the step of introducing the infiltrantmaterial into the diamond body, it may be desirable to introduce anothermaterial, e.g., a replacement material into the diamond body. Thereplacement material is different from the infiltrant material and canbe selected to contribute one or more desired properties to theresulting polycrystalline diamond body. The replacement material can beintroduced by the same techniques noted above for introducing theinfiltrant material, and can fully or partially densify the diamondbody, and can extend through the body to a working surface, depending onthe particular end-use application. Example replacement materialsinclude non-refractory metals, ceramics, silicon and silicon-containingcompounds, ultra-hard materials such as diamond and cBN, and mixturesthereof.

In the event that such replacement material is introduced in the diamondbody, in addition to the infiltrant material, the resulting diamond bodymay include different regions characterized by having the replacementmaterial and/or the infiltrant material disposed within the voids orpores. During the subsequent step of removing a portion of theinfiltrant material from the diamond body, some or all of thereplacement material may also be removed.

It is, therefore, to be understood that within the scope of the appendedclaims, this invention may be practiced otherwise than as specificallydescribed.

1. A method for making a polycrystalline diamond construction comprisingthe steps of: subjecting diamond grains to a high pressure/hightemperature condition in the presence of a catalyst material to form apolycrystalline diamond material comprising a matrix phase of bondedtogether diamond grains and interstitial regions disposed between thediamond grains including the catalyst material; treating thepolycrystalline diamond material to remove the catalyst materialtherefrom to form a diamond body that is substantially free of thecatalyst material used to initially form the polycrystalline diamondmaterial; introducing an infiltrant material into the diamond body,wherein the infiltrant material fills a population of the interstitialregions; and attaching a substrate to the diamond body; wherein afterthe step of treating, a region of the diamond body extending a depthfrom a surface of the diamond body is substantially free of theinfiltrant.
 2. The method as recited in claim 1 wherein during the stepof subjecting, a first substrate is used as a source to introduce thecatalyst material during the high pressure/high temperature condition.3. The method as recited in claim 2 wherein during the step ofattaching, a second substrate having a material makeup different thanthe first substrate is used.
 4. The method as recited in claim 1 whereinduring the step of introducing, the infiltrant material is selected fromGroup VIII of the Periodic table.
 5. The method as recited in claim 1comprising, after the step of introducing, treating the diamond body toremove the infiltrant material from a region of the diamond bodyadjacent the surface.
 6. The method as recited in claim 1 wherein thediamond region substantially free of the infiltrant material extends adepth from the diamond body surface including one or both of a top andside surface.
 7. The method as recited in claim 1 wherein the step oftreating comprises using a leaching agent and is selected from the groupof techniques consisting of using elevated temperature, using elevatedpressure, using ultrasonic energy, and combinations thereof.
 8. Themethod as recited in claim 1 wherein the step of attaching is performedby subjecting the diamond body and substrate to high pressure/hightemperature conditions.
 9. The method as recited in claim 8 wherein thesubstrate is the source of the infiltrant and during the step ofintroducing the diamond body and substrate are subjected to highpressure/high temperature conditions.
 10. A method for making apolycrystalline diamond construction comprising the steps of: forming asintered polycrystalline diamond material comprising a matrix phase ofbonded together diamond grains by subjecting a plurality of diamondgrains to a high pressure/high temperature condition in the presence ofa catalyst material; treating the sintered polycrystalline material toremove the catalyst material therefrom to form a diamond body that issubstantially free of the catalyst material used to form the initiallysintered polycrystalline diamond material; introducing an infiltrantmaterial into the diamond body, the infiltrant material being one ormore metals selected from Group VIII of the Periodic table; and treatingthe diamond body to remove a portion of the infiltrant material from aregion extending a depth from a working surface of the body, wherein theinfiltrant material remains in another region of the body.
 11. Themethod as recited in claim 10 wherein during the step of forming, thecatalyst material is provided by a substrate material that is positionedadjacent the plurality of diamond grains.
 12. The method as recited inclaim 11 wherein during the step of forming, the substrate is attachedto the polycrystalline diamond material.
 13. The method as recited inclaim 11 wherein before the step of treating the diamond body to removea portion of the infiltrant material, a substrate material differentfrom the substrate material used during the step of forming is attachedto the diamond body.
 14. The method as recited in claim 10 whereinduring the step of introducing, the diamond body is subjected to a hightemperature/high pressure process.
 15. The method as recited in claim 14wherein a substrate is attached to the diamond body during the step ofintroducing.
 16. A method for making a polycrystalline diamond cuttingelement used for drilling subterranean formations comprising the stepsof: treating a sintered polycrystalline diamond material to remove acatalyst material therefrom to form a diamond body, the sinteredpolycrystalline diamond material comprising bonded together diamondgrains with the catalyst material disposed within interstitial regionsbetween the diamond grains, the treated diamond body being substantiallyfree of the catalyst material used to form the initially sinteredpolycrystalline diamond material; introducing an infiltrant materialinto the diamond body during a high pressure/high temperature process tofill a population of the interstitial regions; and leaching the diamondbody to remove the infiltrant material from a population of theinterstitial regions while allowing the infiltrant material to remain inanother population of the interstitial regions.
 17. The method asrecited in claim 16 further comprising attaching a substrate to thediamond body.
 18. The method as recited in claim 17 wherein thesubstrate is attached to the diamond body during the high pressure/hightemperature process used during the step of introducing.
 19. The methodas recited in claim 16 wherein during the step of leaching theinfiltrant material is removed from the population of interstitialregions disposed along surfaces of the diamond body selected from thetop surface, the side surface, and combinations thereof.
 20. The methodas recited in claim 16 wherein the population of the interstitial regioncomprising the infiltrant material extends from a region within thediamond body to a substrate interface surface.